Giuseppe Scarlata

Application of principal components analysis to the evaluation and selection of eluent systems for the thin-layer chromatography of basic and neutral drugs

Abstract The R F values of 55 drugs in 40 eluent mixtures are reported. Principal component analysis of these data provides a four-significant-components model, which explains 92% of the total variance. This analysis, showing that the eluent mixtures cluster into different groups according to their information content, provides a reliable criterion for the choice of optimal eluents. Four eluent mixtures of [ethyl acetate—methanol—30% ammonia (85:10:5), cyclohexane—toluene—diethylamine (65:25:10), ethyl acetate—chloroform (50:50) and acetone with the plate dipped in potassium hydroxide solution), chosen on the basis of the above criterion and of the R F reproducibility, provide a two significant principal components model that can be used for the identification of unknown samples.

Conformational analysis of some (E)-α-phenyl-β-(2-thienyl)- and -(2-furyl_acrylic acids

Abstract NMR spectral data of some (E)-α-phenyl-β-(2-thienyl) acrylic acids indicate that these compounds exist in the preferred s-trans conformation. In the case of (E)-α-phenyl-β-(2-furyl)acrylic acids and their methyl esters the presence of only s-cis rotamer has been established.

Reversible photoswitching of stimuli-responsive Si(100) surfaces engineered with an assembled 1 -cyano-1-phenyl-2-[4/-(10-undecenyloxy)phenyl]-ethylene monolayer

Si(100) surfaces were molecularly engineered by covalent linkage of a monolayer of two stilbene-based chromophores, either 1-cyano-1-phenyl-2-[4′-(10-undecenyloxy)phenyl]-ethylene or its chlorine derivative, 1-cyano-1-(4-Cl-phenyl)-2-[4′-(10-undecenyloxy)phenyl]-ethylene. The hybrid systems have been probed by monochromatized angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and atomic force microscopy (AFM) measurements. Results indicated robust covalent linkage of stilbene molecules to the functionalized substrate surfaces. AFM lithography and contact angle (CA) analysis confirmed that the adopted molecular architectures proved to be well-suited for reversible cis–trans photoswitching promoted by UV irradiation in the solid state.

High field NMR techniques and molecular modelling study of the inclusion complexes of the nootropic drug tenilsetam (CAS-997) in cyclodextrins

The inclusion complexes of the chiral anti-amnesic drug 3-(2-thienyl)piperazin-2-one (Tenilsetam, CAS-997) with α-, β- and γ-cyclodextrins (CDs) were studied by high resolution 1H NMR spectroscopy and molecular modelling (MACROMODEL interactive computer program). The partial inclusion of the guest from the secondary hydroxyl side of α-CD was observed in aqueous solution, as well as a deeper insertion into β-CD from the same side; no interactions were evidenced with γ-CD. Diastereoisomeric pairs were observed for both α- and β-CD inclusion complexes. ROESY experiments allowed us to detect the dipolar contacts between protons of the thiophene ring and those of the internal cavity of β-CD. The possible geometry of the complex edifice derived from experimental results was consistent with those obtained by molecular modelling. The formation of hydrogen bonds provides specific interaction sites to differentiate the diastereoisomeric intermolecular inclusion complexes in terms of conformational host–guest adaptation according to available experimental NMR data.

High field NMR techniques, molecular modelling and molecular dynamics simulations in the study of the inclusion complex of the cognition activator (±)-1-(4-methoxybenzoyl)-5-oxo-2-pyrrolidinepropanoic acid (CI-933) with β-cyclodextrin

Abstract The formation of the inclusion complex of β-cyclodextrin with the new cognition activator (±)-1-(4-methoxybenzoyl)-5-oxo-2-pyrrolidinepropanoic acid (CI-933) and the chiral discrimination capability of the macrocyclic host towards the racemic guest were evident from 1H NMR studies. The structure, relative host-guest orientation and binding mode of the complex were studied using the ROESY NMR technique complemented by molecular modelling and molecular dynamics simulations ( charmm ). All these methods converged towards the structure attained by inserting the guest, the aromatic ring first, into the hydrophobic cavity of the host from the side of the secondary hydroxyls. Both the R- and S-enantiomers were found deeply inserted into the host, the diastereoisomeric complexes formed featuring different numbers and distribution of intermolecular hydrogen bonds.

Infrared and ultraviolet spectra of some 2-thiophenecarboxamides

Abstract The i.r. spectra of some 2-thiophene-carboxamides have been investigated for identification of the N-H stretching, CO stretching and N-H deformation bands. The u.v. spectra have been recorded in order to get information about the chromophores responsible for absorption.

On the conformation of some (Z)-2-styrylfuranes and -thiophenes

Abstract A u.v. study of some (E) and (Z)-2-styrylfuranes and -thiophenes has been accomplished. The data are consistent with the hypothesis of a s-trans preferred conformation for the (Z) isomers. A correlation between frequency shifts (ν(Z)-ν(E) and Hammett σ constants shows a greater sensitivity of thiophene ring to substituent.

A simple H1 NMR approach to the conformations of α,β-diarylacrylonitriles☆

Abstract Room temperature 60 MHz NMR data of α,β-diarylacrylonitriles were interpreted in a search for a method for routine stereochemical assignments and to establish the conformational preferences of the β-heterocyclic ring. The conformation of the α-phenyl group differs from that of diaryl ethylenes previously investigated. Solvent effect on the conformations is observed only for pyrrole derivatives.

Photoelectron He(I) spectroscopic study of diphenyl sulphide, diphenyl sulphone and their mono- and di-2-pyridyl analogues

The He(I) photoelectron spectra of diphenylsulphide, 2-pyridylphenylsulphide, and di-2-pyridyl-sulphide and related sulphones are reported. An interpretation of the lower energy bands is given on a correlative basis from those of simple related molecules and in terms of perturbational m.o. analysis and the inductive effect of the SO2 substituent.

Infrared and ultraviolet spectra of some (Z)-α-phenyl-β(2-thienyl) acrylonitriles

Abstract The i.r. spectra of some ( Z )-α-( p -substituted-phenyl)-β-(5-substituted-2-thienyl)acrylonitriles have been investigated for the identification of the main absorption frequencies of cyano, ethylenic and thienyl groups. The u.v. spectra have been discussed in order to obtain further information about the chromophores responsible for the absorption.